FIX: Use previous chunk to check if local backup chunk upload complete (#14896)

Uppy and Resumable slice up their chunks differently, which causes a difference
in this algorithm. Let's take a 131.6MB file (137951695 bytes) with a 5MB (5242880 bytes)
chunk size. For resumable, there are 26 chunks, and uppy there are 27. This is
controlled by forceChunkSize in resumable which is false by default. The final
chunk size is 6879695 (chunk size + remainder) whereas in uppy it is 1636815 (just remainder).

This means that the current condition of uploaded_file_size + current_chunk_size >= total_size
is hit twice by uppy, because it uses a more correct number of chunks. This
can be solved for both uppy and resumable by checking the _previous_ chunk
number * chunk_size as the uploaded_file_size.

An example of what is happening before that change, using the current
chunk number to calculate uploaded_file_size.

chunk 26: resumable: uploaded_file_size (26 * 5242880) + current_chunk_size (6879695) = 143194575 >= total_size (137951695) ? YES
chunk 26: uppy: uploaded_file_size (26 * 5242880) + current_chunk_size (5242880) = 141557760 >= total_size (137951695) ? YES
chunk 27: uppy: uploaded_file_size (27 * 5242880) + current_chunk_size (1636815) = 143194575 >= total_size (137951695) ? YES

An example of what this looks like after the change, using the previous
chunk number to calculate uploaded_file_size:

chunk 26: resumable: uploaded_file_size (25 * 5242880) + current_chunk_size (6879695) = 137951695 >= total_size (137951695) ? YES
chunk 26: uppy: uploaded_file_size (25 * 5242880) + current_chunk_size (5242880) = 136314880 >= total_size (137951695) ? NO
chunk 27: uppy: uploaded_file_size (26 * 5242880) + current_chunk_size (1636815) = 137951695 >= total_size (137951695) ? YES

app/controllers/admin/backups_controller.rb

@@ -176,13 +176,14 @@ class Admin::BackupsController < Admin::AdminController
     chunk_number = params.fetch(:resumableChunkNumber).to_i
     chunk_size = params.fetch(:resumableChunkSize).to_i
     current_chunk_size = params.fetch(:resumableCurrentChunkSize).to_i
+    previous_chunk_number = chunk_number - 1
 
     # path to chunk file
     chunk = BackupRestore::LocalBackupStore.chunk_path(identifier, filename, chunk_number)
     # upload chunk
     HandleChunkUpload.upload_chunk(chunk, file: file)
 
-    uploaded_file_size = chunk_number * chunk_size
+    uploaded_file_size = previous_chunk_number * chunk_size
     # when all chunks are uploaded
     if uploaded_file_size + current_chunk_size >= total_size
       # merge all the chunks in a background thread

spec/requests/admin/backups_controller_spec.rb

@@ -234,10 +234,10 @@ RSpec.describe Admin::BackupsController do
 
     describe "when filename is valid" do
       it "should upload the file successfully" do
+        freeze_time
         described_class.any_instance.expects(:has_enough_space_on_disk?).returns(true)
 
         filename = 'test_Site-0123456789.tar.gz'
-        @paths = [backup_path(File.join('tmp', 'test', "#{filename}.part1"))]
 
         post "/admin/backups/upload.json", params: {
           resumableFilename: filename,
@@ -248,11 +248,102 @@ RSpec.describe Admin::BackupsController do
           resumableCurrentChunkSize: '1',
           file: fixture_file_upload(Tempfile.new)
         }
+        expect_job_enqueued(job: :backup_chunks_merger, args: {
+          filename: filename, identifier: 'test', chunks: 1
+        }, at: 5.seconds.from_now)
 
         expect(response.status).to eq(200)
         expect(response.body).to eq("")
       end
     end
+
+    describe "completing an upload by enqueuing backup_chunks_merger" do
+      let(:filename) { 'test_Site-0123456789.tar.gz' }
+
+      it "works with a single chunk" do
+        freeze_time
+        described_class.any_instance.expects(:has_enough_space_on_disk?).returns(true)
+
+        # 2MB file, 2MB chunks = 1x 2MB chunk
+        post "/admin/backups/upload.json", params: {
+          resumableFilename: filename,
+          resumableTotalSize: '2097152',
+          resumableIdentifier: 'test',
+          resumableChunkNumber: '1',
+          resumableChunkSize: '2097152',
+          resumableCurrentChunkSize: '2097152',
+          file: fixture_file_upload(Tempfile.new)
+        }
+        expect_job_enqueued(job: :backup_chunks_merger, args: {
+          filename: filename, identifier: 'test', chunks: 1
+        }, at: 5.seconds.from_now)
+      end
+
+      it "works with multiple chunks when the final chunk is chunk_size + remainder" do
+        freeze_time
+        described_class.any_instance.expects(:has_enough_space_on_disk?).twice.returns(true)
+
+        # 5MB file, 2MB chunks = 1x 2MB chunk + 1x 3MB chunk with resumable.js
+        post "/admin/backups/upload.json", params: {
+          resumableFilename: filename,
+          resumableTotalSize: '5242880',
+          resumableIdentifier: 'test',
+          resumableChunkNumber: '1',
+          resumableChunkSize: '2097152',
+          resumableCurrentChunkSize: '2097152',
+          file: fixture_file_upload(Tempfile.new)
+        }
+        post "/admin/backups/upload.json", params: {
+          resumableFilename: filename,
+          resumableTotalSize: '5242880',
+          resumableIdentifier: 'test',
+          resumableChunkNumber: '2',
+          resumableChunkSize: '2097152',
+          resumableCurrentChunkSize: '3145728',
+          file: fixture_file_upload(Tempfile.new)
+        }
+        expect_job_enqueued(job: :backup_chunks_merger, args: {
+          filename: filename, identifier: 'test', chunks: 2
+        }, at: 5.seconds.from_now)
+      end
+
+      it "works with multiple chunks when the final chunk is just the remaninder" do
+        freeze_time
+        described_class.any_instance.expects(:has_enough_space_on_disk?).times(3).returns(true)
+
+        # 5MB file, 2MB chunks = 2x 2MB chunk + 1x 1MB chunk with uppy.js
+        post "/admin/backups/upload.json", params: {
+          resumableFilename: filename,
+          resumableTotalSize: '5242880',
+          resumableIdentifier: 'test',
+          resumableChunkNumber: '1',
+          resumableChunkSize: '2097152',
+          resumableCurrentChunkSize: '2097152',
+          file: fixture_file_upload(Tempfile.new)
+        }
+        post "/admin/backups/upload.json", params: {
+          resumableFilename: filename,
+          resumableTotalSize: '5242880',
+          resumableIdentifier: 'test',
+          resumableChunkNumber: '2',
+          resumableChunkSize: '2097152',
+          resumableCurrentChunkSize: '2097152',
+          file: fixture_file_upload(Tempfile.new)
+        }
+        post "/admin/backups/upload.json", params: {
+          resumableFilename: filename,
+          resumableTotalSize: '5242880',
+          resumableIdentifier: 'test',
+          resumableChunkNumber: '3',
+          resumableChunkSize: '2097152',
+          resumableCurrentChunkSize: '1048576',
+          file: fixture_file_upload(Tempfile.new)
+        }
+        expect_job_enqueued(job: :backup_chunks_merger, args: {
+          filename: filename, identifier: 'test', chunks: 3
+        }, at: 5.seconds.from_now)
+      end
+    end
   end
 
   describe "#check_backup_chunk" do